The present invention relates to the medical diagnostic imaging and minimally invasive stereotactic surgery arts. It finds particular application in conjunction with an integrated CT scanner and mechanically guided surgical instruments and will be described with particular reference thereto. It is to be appreciated, however, that the invention is also applicable to guiding surgical instruments in conjunction with magnetic resonance, ultrasonic, and other imaging systems.
It is often desired that interventional medical procedures be as minimally invasive as possible. However, it is also desirable to be able to visualize or otherwise know the relative positions and/or orientations of surgical tools or devices with respect to surrounding anatomy. The latter goal may be achieved by a direct inspection of the anatomy. However, in the case of interior anatomy, direct inspection may be more invasive than desired since relatively large incisions may have to be made to expose or access the interior anatomy for direct inspection.
For example, it is often desirable to sample or test a portion of tissue from human or animal subjects, particularly in the diagnosis and treatment of potentially cancerous tumors, pre-malignant conditions, and other diseases or disorders. Typically, in the case of tumors, when the physician suspects that cancer or an otherwise diseased condition exists, a biopsy is performed to determine if in fact cells from the tumor are cancerous or otherwise diseased. Many biopsies, such as percutaneous biopsies, are performed with a needle-like instrument used to collect the cells for analysis.
In recent years, the performance of interventional medical procedures such as needle biopsies has been enhanced by the use of x-ray imaging, CT scans, continuous CT (CCT), magnetic resonance imaging (MRI), fluoroscopy, single photon emission CT (SPECT), positron emission tomography (PET), and the like. The imaging equipment allows an interventionalist, such as a radiologist, surgeon, physician, or other medical personnel, to track the insertion of interventional devices, such as biopsy needles, in a subject during diagnostic and therapeutic procedures. While such imaging modalities allow procedures to be performed with minimal invasiveness and are helpful to the interventionalist and the patient, they have certain drawbacks.
For example, with some image-guided procedures, e.g., those using CT imaging, the tracking of the needle position is not done in real-time. That is to say, a static image is obtained and the needle position noted therein. Subsequently, the needle is advanced or retracted by a small amount and another static image obtained to verify the new needle position. This sequence is repeated as many times as necessary to track the needle's progression. Such a procedure tends to be time consuming insomuch as the needle progresses by only a short distance or increment between imaging, and needle progression is halted during imaging. Moreover, accuracy suffers to the extent that in the interim, i.e., between images, the needle's position cannot be visualized.
With the development of CCT imaging and fluoroscopy, real-time imaging has been made possible. In CCT scanning, a rotating x-ray source irradiates the subject continuously, generating images at a rate of approximately six frames per second. The use of CCT or fluoroscopy by the interventionalist for real-time guidance and/or tracking of the needle during biopsies is gaining popularity. As a result, biopsies have become not only more accurate, but also shorter in duration.
Heretofore, several surgical instrument guidance devices have been proposed for use in conjunction with a CT scanner to allow a user to accurately place a catheter, drainage tube, or biopsy probe within a patient's body. U.S. Pat. No. 4,733,661 describes a hand held guidance device including a planar base with a bubble level to maintain the base in a horizontal position. Needle guides are provided on a support arm pivotally secured to the base, the guides slidingly supporting a catheter at a desired angle as the catheter into the patient's body. The guidance device includes a reference line formed upon the base adapted to be aligned with a transverse light beam projected by the CT scanner apparatus. Although it may be possible for the device to be used to accurately insert a biopsy needle within a patient's body without damage to any unintended targets, one major disadvantage of the device is its reliance upon an accurate human alignment between the reference line defined on the base of the device and the transverse light beam projected by the CT scanner. It would, therefore, be desirable to provide a surgical instrument guidance device which is not dependent upon a manual alignment step.
U.S. Pat. No. 4,583,538 proposes a free standing biopsy guide that is adapted to hold needles or probes at various selectable calculated angles. In using the device proposed in that patent, a reference point on the patient's body is found that exactly correlates to a point on the CT scan. This is accomplished by means of a localization device placed on the patient's skin which can be identified in cross section on the CT scan. Measurements of the localization device on the CT scan are then correlated to the device on the patient. The free standing biopsy guide is then adjusted according to those calculations. One disadvantage of the device taught by this patent is the time required to correlate the patient body reference point with selected points on the CT scan. In addition, certain inaccuracies may be introduced during the point correlation step and while adjusting the free standing guidance device. Accordingly, it would be desirable to provide a biopsy or other surgical instrument guide that is affixed in a known position relative to the CT scanner apparatus whereby precise and automatic correlation between the coordinate systems of the guidance device, patient table, and patient image volume are automatically established.
Another drawing to prior mechanical linkage-type systems relates to the fact that they typically move the needle, or other surgical instrument, along a straight line. Maintaining a straight line can be problematic if the distance to be traveled, i.e. the depth of insertion, by the biopsy needle is large. It is therefore desirable that the mechanical system is able to grip, insert, release, and distally re-grip the biopsy needle for further insertion during an interventional procedure. In this manner, the range of motion of the mechanical system is relatively small, and linear, while the depth of the needle insertion is relatively large.
The present invention provides a new and improved interchangeable surgical instrument guidance device and method for using same which overcomes the above-referenced problems and others.